The present invention relates to a control device that controls torque generation of an induction motor with high precision.
Conventionally, a vector control method is used in induction motors to drive the induction motors with high precision. The vector control method is a method of controlling a d-axis current and a q-axis current on the rotation coordinate axes (d-q axes) that rotate in synchronism with a secondary magnetic flux to respectively desired values. Generally, it is impossible to directly observe the secondary magnetic flux due to hardware limitations. Therefore, there is proposed a sliding frequency vector controlling method in which secondary magnetic flux is estimated based upon a primary current of the induction motor.
However, in this sliding frequency vector controlling method, a value of a secondary resistance is required for calculating the secondary magnetic flux. Therefore, there arises a problem that, changes in the secondary resistance due to heat generation, etc. would cause degradation in the controlling performance.
FIG. 12 is a graph which is obtained by plotting the relationship between the torque instruction and the torque error in a conventional control device for an induction motor to which the sliding frequency vector controlling system is applied. In FIG. 12, the abscissa represents the torque instruction, and the ordinate represents the torque error (=generated torque-torque instruction). The graph in the upper half of the FIG. 12 represents the relationship between the torque instruction and the torque error when the rotation speed is 3 [rad/s], and the graph in the lower half represents the relationship between the torque instruction and the torque error when the rotation speed is 188 [rad/s]. Moreover, the solid line shows the characteristic obtained when the secondary resistance of the induction motor has increased by a factor of 1.3, and the broken line shows the characteristic obtained when the secondary resistance of the induction motor has decreased by a factor of {fraction (1/1.3)}.
As shown in FIG. 12, in the conventional control device for the induction motor to which the sliding frequency vector controlling system has been applied, there arises a problem that, when the value of the secondary resistance changes, a torque error is generated irrespective of the rotation speed.
A method which identifies a secondary resistance value during the driving operation of the induction motor has been proposed. However, depending on driving conditions, the estimated value of the secondary resistance is dispersed, resulting in problems with respect to the stability.
In order to solve these problems, a control device for an induction motor including a magnetic flux observing device, which calculates the secondary magnetic flux based upon the primary current and the primary voltage of the induction motor, and to which the induction motor constant is applied, has been proposed.
For example, FIG. 13 is a structural diagram which shows a prior art control device for an induction motor shown in a document xe2x80x9cIndirect Field Oriented Control Method Using Flux Observer Equivalent To The Direct Field Oriented Control Methodxe2x80x9d (1992 National Convention Record of the IEE Japan-Industry Application Society, No.110 (pp. 466-471).
The principle of controlling by the prior art control device for an induction motor will be explained. The magnetic flux observing device, which is constituted on stationary bi-axes (xcex1-xcex2 axes), is designed based upon the following equations (1) and (2).                                           ⅆ                          ⅆ              t                                ⁢                      (                                                                                                      i                      ^                                                              α                      ⁢                                              xe2x80x83                                            ⁢                      s                                                                                                                                                              i                      ^                                                              β                      ⁢                                              xe2x80x83                                            ⁢                      s                                                                                            )                          =                                            A              11                        ⁡                          (                                                                                                                  i                        ^                                                                    α                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                                                                                                i                        ^                                                                    β                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                        )                                +                                    A              12                        ⁡                          (                                                                                                                  φ                        ^                                                                    α                        ⁢                                                  xe2x80x83                                                ⁢                        r                                                                                                                                                                                φ                        ^                                                                    β                        ⁢                                                  xe2x80x83                                                ⁢                        r                                                                                                        )                                +                      B            ⁡                          (                                                                                          v                                              α                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                                                                        v                                              β                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                        )                                +                                    K              1                        ⁡                          (                                                                                                                                            i                          ^                                                                          α                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                                                  α                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                                                                                                                                                                                  i                          ^                                                                          β                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                                                  β                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                                                                                )                                                          (        1        )                                                      ⅆ                          ⅆ              t                                ⁢                      (                                                                                                      φ                      ^                                                              α                      ⁢                                              xe2x80x83                                            ⁢                      r                                                                                                                                                              φ                      ^                                                              β                      ⁢                                              xe2x80x83                                            ⁢                      r                                                                                            )                          =                                            A              21                        ⁡                          (                                                                                                                  i                        ^                                                                    α                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                                                                                                i                        ^                                                                    β                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                        )                                +                                    A              22                        ⁡                          (                                                                                                                  φ                        ^                                                                    α                        ⁢                                                  xe2x80x83                                                ⁢                        r                                                                                                                                                                                φ                        ^                                                                    β                        ⁢                                                  xe2x80x83                                                ⁢                        r                                                                                                        )                                +                                    K              2                        ⁡                          (                                                                                                                                            i                          ^                                                                          α                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                                                  α                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                                                                                                                                                                                  i                          ^                                                                          β                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                                                  β                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                                                                                )                                                          (        2        )            
where,             A      11        =          (                                                  -                              (                                                                            R                      s                                                              σ                      ⁢                                              xe2x80x83                                            ⁢                                              L                        s                                                                              +                                                                                    R                        r                                            ⁡                                              (                                                  1                          -                          σ                                                )                                                                                    σ                      ⁢                                              xe2x80x83                                            ⁢                                              L                        r                                                                                            )                                                                                        xe2x80x83                            ⁢              0                                                            0                                              -                              (                                                                            R                      s                                                              σ                      ⁢                                              xe2x80x83                                            ⁢                                              L                        s                                                                              +                                                                                    R                        r                                            ⁡                                              (                                                  1                          -                          σ                                                )                                                                                    σ                      ⁢                                              xe2x80x83                                            ⁢                                              L                        r                                                                                            )                                                        )                  A      12        =          (                                                                  MR                r                                            σ                ⁢                                  xe2x80x83                                ⁢                                  L                  s                                ⁢                                  L                  r                  2                                                                                                                          P                  m                                ⁢                                  ω                  m                                ⁢                M                                            σ                ⁢                                  xe2x80x83                                ⁢                                  L                  s                                ⁢                                  L                  r                                                                                                        -                              xe2x80x83                            ⁢                                                                    P                    m                                    ⁢                                      ω                    m                                    ⁢                  M                                                  σ                  ⁢                                      xe2x80x83                                    ⁢                                      L                    s                                    ⁢                                      L                    r                                                                                                                          MR                r                                            σ                ⁢                                  xe2x80x83                                ⁢                                  L                  s                                ⁢                                  L                  r                  2                                                                        )                  A      21        =          (                                                                  MR                r                                            L                r                                                          0                                                0                                                              MR                r                                            L                r                                                        )                  A      22        =          (                                                  -                              xe2x80x83                            ⁢                                                R                  r                                                  L                  r                                                                                                        -                                  P                  m                                            ⁢                              ω                m                                                                                                        P                m                            ⁢                              ω                m                                                                        -                              xe2x80x83                            ⁢                                                R                  r                                                  L                  r                                                                        )            B    =          (                                                  1                              σ                ⁢                                  xe2x80x83                                ⁢                                  L                  s                                                                          0                                                0                                              1                              σ                ⁢                                  xe2x80x83                                ⁢                                  L                  s                                                                        )      
In order to place the pole of the magnetic flux observing device on a conjugate complex pole or a duplex pole, square matrixes K1, K2 are defined by using equations (3) and (4), and k1, k2, k3, k4 are determined according to the rotation speed.                               K          1                =                  (                                                                      k                  1                                                                              -                                      k                    2                                                                                                                        k                  2                                                                              k                  1                                                              )                                    (        3        )                                          K          2                =                  (                                                                      k                  3                                                                              -                                      k                    4                                                                                                                        k                  4                                                                              k                  3                                                              )                                    (        4        )            
Therefore, when equation (1) is coordinate-converted onto rotation axes (d-q axes) with equation (2) being coordinate-converted onto the stator polar coordinates, equations (5) to (7) are obtained.                                           ⅆ                          ⅆ              t                                ⁢                      (                                                                                                      i                      ^                                                              d                      ⁢                                              xe2x80x83                                            ⁢                      s                                                                                                                                                              i                      ^                                                              q                      ⁢                                              xe2x80x83                                            ⁢                      s                                                                                            )                          =                                                            A                ~                            11                        ⁡                          (                                                                                                                  i                        ^                                                                    d                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                                                                                                i                        ^                                                                    q                        ⁢                                                  xe2x80x83                                                ⁢                        s                                                                                                        )                                +                                    (                                                                                                                  MR                        r                                                                    σ                        ⁢                                                  xe2x80x83                                                ⁢                                                  L                          s                                                ⁢                                                  L                          r                          2                                                                                                                                                                                -                                              xe2x80x83                                            ⁢                                                                                                    P                            m                                                    ⁢                                                      ω                            m                                                    ⁢                          M                                                                          σ                          ⁢                                                      xe2x80x83                                                    ⁢                                                      L                            s                                                    ⁢                                                      L                            r                                                                                                                                                          )                        ⁢                                          φ                ^                            ds                                +                      B            ⁡                          (                                                                                          v                      ds                                                                                                                                  v                      qs                                                                                  )                                -                                    K              1                        ⁡                          (                                                                                                                                            i                          ^                                                                          d                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                        ds                                                                                                                                                                                                          i                          ^                                                                          q                          ⁢                                                      xe2x80x83                                                    ⁢                          s                                                                    -                                              i                        qs                                                                                                        )                                                          (        5        )                                                      ⅆ                          ⅆ              t                                ⁢                                    φ              ^                        dr                          =                                            -                              xe2x80x83                            ⁢                                                R                  r                                                  L                  r                                                      ⁢                                          φ                ^                            dr                                +                                                    MR                r                                            L                r                                      ⁢                                          i                ^                            ds                                -                      (                                                            k                  3                                ⁡                                  (                                                                                    i                        ^                                            ds                                        -                                          i                      ds                                                        )                                            -                                                k                  4                                ⁡                                  (                                                                                    i                        ^                                            qs                                        -                                          i                      qs                                                        )                                                      )                                              (        6        )                                                      ⅆ                          ⅆ              t                                ⁢                                    θ              ^                        ⁡                          (                              =                ω                            )                                      =                                            P              m                        ⁢                          ω              m                                +                                                    MR                r                                            L                r                                      ⁢                          xe2x80x83                        ⁢                                                            i                  ^                                qs                                                              φ                  ^                                dr                                              -                      xe2x80x83                    ⁢                                                                      k                  4                                ⁡                                  (                                                                                    i                        ^                                            ds                                        -                                          i                      ds                                                        )                                            +                                                k                  3                                ⁡                                  (                                                                                    i                        ^                                            qs                                        -                                          i                      qs                                                        )                                                                                    φ                ^                            dr                                                          (        7        )            
where the following equation is satisfied.             A      ~        11    =            A      11        -          (                                    0                                              -              ω                                                            ω                                0                              )      
In other words, based upon equations (5) to (7), magnetic flux calculations that are equivalent to the magnetic flux observing device on the xcex1-xcex2 axes can be obtained on the d-q axes.
With respect to the two square matrixes K1, K2, those that have been designed on the stationary bi-axes are applied. In other words, square matrixes K1, K2 are defined by equation (3) and equation (4), and according to rotation speeds, k1, k21, k3 and k4 are determined. In this case, between K1 and K2, the relationship represented by equation (8) is always satisfied.
K1K2=K2K1xe2x80x83xe2x80x83(8)
Here, the relationship between mutually commutative matrixes K1, K2 refers to the relationship satisfying a commutative rule. Here, equations (5) to (7) can be rewritten to equations (9) to (13).                               (                                                                      z                  1                                                                                                      z                  2                                                              )                =                              K            1                    ⁡                      (                                                                                                                              i                        ^                                            ds                                        -                                          i                      ds                                                                                                                                                                                      i                        ^                                            qs                                        -                                          i                      qs                                                                                            )                                              (        9        )                                          (                                                                      z                  3                                                                                                      z                  4                                                              )                =                              K            2                    ⁡                      (                                                                                                                              i                        ^                                            ds                                        -                                          i                      ds                                                                                                                                                                                      i                        ^                                            qs                                        -                                          i                      qs                                                                                            )                                              (        10        )                                                      ⅆ                          ⅆ              t                                ⁢                      (                                                                                                      i                      ^                                        ds                                                                                                                                          i                      ^                                        qs                                                                        )                          =                                                            A                ~                            11                        ⁡                          (                                                                                                                  i                        ^                                            ds                                                                                                                                                          i                        ^                                            qs                                                                                  )                                +                                    (                                                                                                                  MR                        r                                                                    σ                        ⁢                                                  xe2x80x83                                                ⁢                                                  L                          s                                                ⁢                                                  L                          r                          2                                                                                                                                                                                -                                              xe2x80x83                                            ⁢                                                                                                    P                            m                                                    ⁢                                                      ω                            m                                                    ⁢                          M                                                                          σ                          ⁢                                                      xe2x80x83                                                    ⁢                                                      L                            s                                                    ⁢                                                      L                            r                                                                                                                                                          )                        ⁢                                          φ                ^                            ds                                +                      B            ⁡                          (                                                                                          v                      ds                                                                                                                                  v                      qs                                                                                  )                                -                      (                                                                                z                    1                                                                                                                    z                    2                                                                        )                                              (        11        )                                                      ⅆ                          ⅆ              t                                ⁢                                    φ              ^                        dr                          =                                            -                              xe2x80x83                            ⁢                                                R                  r                                                  L                  r                                                      ⁢                                          φ                ^                            dr                                +                                                    MR                r                                            L                r                                      ⁢                                          i                ^                            ds                                -                      z            3                                              (        12        )                                                      ⅆ                          ⅆ              t                                ⁢                                    θ              ^                        ⁡                          (                              =                ω                            )                                      =                                            P              m                        ⁢                          ω              m                                +                      (                                                                                MR                    r                                                        L                    r                                                  ⁢                                                      i                    ^                                    qs                                            -                              z                4                                      )                    +                                    φ              ^                        dr                                              (        13        )            
Therefore, based upon equations (9) to (13), it is possible to obtain the phase and amplitude of an estimated secondary magnetic flux with the same precision as a magnetic flux observing device that is constituted on the stationary bi-axes (xcex1-xcex2 axes). Thus, by controlling the d-axis current and the q-axis current to respectively desired different values based upon this phase, it becomes possible to suppress degradation in the control performance due to the secondary resistance change.
The construction of a conventional control device for an induction motor shown in FIG. 13 will be explained. This control device for the induction motor 1 is provided with a rotation speed detector 2, a current detector 3, a magnetic flux observing device 4, a control unit 5, an amplifying unit 6 and a coordinate converter 7 which coordinate-converts a primary current obtained from the current detector 2 onto a rotary coordinate axes (d-q axes) based upon the phase {circumflex over (xcex8)} of the estimated secondary magnetic flux. Moreover, the control unit 5 is provided with a current control device 8, a coordinate converter 9 and a PWM inverter 10.
The amplifying unit 6 is provided with subtracters 11, 12, gain calculators 13, 14. The rotation speed detector 2 detects the rotation speed xcfx89m of the induction motor 1, and the current detector 3 detects primary currents ius, ivs of the induction motor 1.
Based upon primary voltage instructions Vds*, Vqs* to be applied to the induction motor 1 and deviation signals Z1, Z2, Z3, Z4 obtained from the amplifying unit 6, the magnetic flux observing device 4 estimates the amplitude {circumflex over ("PHgr")}dk of the estimated secondary magnetic flux, the phase {circumflex over (xcex8)}of the estimated secondary magnetic flux, the d-axis component ids of the estimated primary current and the q-axis component, iqs of the estimated primary current in the induction motor 1.
Based upon the phase {circumflex over (xcex8)}of the estimated secondary magnetic flux obtained by the magnetic flux observing device 4, the control unit 5 controls the voltage to be applied to the induction motor 1 so that the primary current is made coincident with a desired current given on the d-q axes. In other words, the current control device 8 outputs primary voltage instructions Vds*, Vqs* onto the d-q axes so that the d-axis primary current ids, q-axis primary current iqs are respectively made coincident with desired currents (d-axis primary current instruction ids*, q-axis primary current instruction iqs*) given on the d-q axes, and based upon the phase {circumflex over (xcex8)}of the estimated secondary magnetic flux, the coordinate converter 9 calculates three-phase voltage instructions Vus*, Vvs*, V,ws*. Based upon these three-phase voltage instructions Vus*, Vvs*, Vws*, the PWM inverter 10 applies three-phase voltages Vus, Vvs, Vws to the induction motor 1.
The amplifying unit 6 obtains the output of the current detector 3 as a primary current on the d-q axes via the coordinate converter 7, and amplifies the deviation of the estimated primary current on the d-q axes obtained from the magnetic flux observing device 4 and the primary current on the primary current on the d-q axes based upon the two square matrixes K1, K2, and outputs the resulting signals as deviation signals Z1, Z2, Z3, Z4.
In other words, the subtracter 11 calculates the deviation îds-ids between the d-axis estimated primary current îds obtained from the magnetic flux observing device 4 and d-axis primary current ids obtained from the coordinate converter 7. The subtracter 12 calculates the deviation îqs-iqs between the q-axis estimated primary current îqs obtained from the magnetic flux observing device 4 and q-axis primary current îqs obtained from the coordinate converter 7. The gain calculator 13 calculates deviation signals Z1, Z2 based upon the first square matrix K1 of equation (9), and the gain calculator 14 calculates deviation signals Z3, z4 based upon the second square matrix K2. Here, since the first square matrix and the second square matrix are functions of the rotation speed, the gain calculators 13, 14 provide functions of the rotation speed obtained from the rotation speed detector 2.
FIG. 14 is a drawing which shows an inner construction of the magnetic flux observing device 4. The magnetic flux observing device 4 is provided with matrix calculators 15 to 17, gain calculators 18 to 21, integrators 22 to 25, adders 26 to 30, an adder-subtracter 31, subtracters 32 to 34 and a divider 35.
The gain calculator 21 multiplies the output xcfx89m of the rotation speed detector 2 by Pm to output Pmxc2x7xcfx89m. The gain calculator 16 to which the output îds of the integrator 22 and the output îqs of the integrator 23 are input calculates the first term on the right-hand side of equation (11) based upon the output xcfx89 of the adder 30. The gain calculator 17 to which the output {circumflex over ("PHgr")}dr of the integrator 24 is input calculates the second term on the right-hand side of equation (11) based upon the output Pmxc2x7xcfx89m of the gain calculator 21. The gain calculator 15 to which the primary voltage instructions Vds*, Vqs* obtained from the control unit 5 are input calculates the third term on the right-hand side of equation (11).
The right-hand side of equation (11) is calculated by the adders 26, 27, 28, 29 and the subtracters 33, 34, and the resulting differentiation values îds, îqs are input to the integrators 22, 23. The integrators 22, 23 respectively integrate the differentiation values îds, îqs, and outputs values îds, îqs.
The gain calculator 19 to which the output {circumflex over ("PHgr")}dr of the integrator 24 is input calculates the first term on the right-hand side of equation (12). The gain calculator 18 to which the output îds of the integrator 22 is input calculates the second term on the right-hand side of equation (12). The adder-subtracter 31 calculates the right-hand side of equation (12) to input the differentiation value of {circumflex over ("PHgr")}dr to the integrator 24. The integrator 24 integrates the differentiation value of {circumflex over ("PHgr")}dr to output {circumflex over ("PHgr")}dr.
The gain calculator 20, the subtracter 32 and the divider 35 are used to calculate the second term of the right-hand side of equation (13). The adder 30 calculates the right-hand side of equation (13) to output the differentiation value of {circumflex over (xcex8)}, that is, xcfx89. The integrator 25 integrates the output xcfx89 of the adder 30 to output {circumflex over (xcex8)}.
In this manner, based upon the rotation speed obtained from the rotation speed detector 2, the primary voltage instructions Vds*, Vqs* of the induction motor 1 and the deviation signals Z1, Z2, Z3, Z4 obtained from the amplifying unit 6, the magnetic flux observing device 4 calculates the estimated secondary magnetic fluxes {circumflex over ("PHgr")}dr, {circumflex over (xcex8)} and the estimated primary current îds, îqs.
FIG. 15 is a graph in which the relationship between the torque instruction and the torque error in a conventional control device of an induction motor to which the magnetic flux observing device shown in FIGS. 13 and 14 are applied is plotted. In FIG. 15, the abscissa represents the torque instruction, and the ordinate represents the torque error (=generated torque-torque instruction). The graph in the upper half of FIG. 15 shows a state in which the rotation speed is set to 3 [rad/s] and the graph in the lower half of FIG. 15 shows a state in which it is set to 188 [rad/s]. Moreover, the solid line represents a characteristic when the secondary resistance of the induction motor 1 has increased by a factor of 1.3, and the broken line represents a characteristic when the secondary resistance of the induction motor 1 has reduced by a factor of 1/1.3.
As shown by comparisons between FIG. 12 and FIG. 15, in comparison with the control device of an induction motor to which the sliding frequency vector control system is applied, the conventional control device of an induction motor to which the magnetic flux observing device shown in FIGS. 13 and 14 is applied makes it possible to reduce the torque error in the instance of the rotation frequency of 188 [rad/s] without the necessity of estimating the secondary resistance during the driving of the induction motor 1.
However, a problem has been raised in which, in a low-speed range such as 3 [rad/s] in the rotation frequency, it exerts only small effects. The reason for this is as follows. In the conventional control device of an induction motor, since there is a limitation that, upon designing two square matrixes K1 and K2 of the amplifying unit 6, K1 and K2 need to be mutually variable, the effects of the induction motor constant error to resistors, etc. cannot be suppressed optimally.
In particular, in general, electric vehicles such as electric cars are driven by torque control, and during the driving of an electric car, the greatest torque is required at the time of activating the car and stopping the car. Therefore, in a range with the speed being close to zero, it is required to provide a torque control with high precision in both of the generating and re-generating operations.
Moreover, in a printing machine, machine parts are connected to a motor through many gears. Therefore, at the time of activation, the motor is initially rotated at a minimum speed and gradually rotated at higher speeds. In this case, variations in the precision in torque control would cause variations in the speed response in controlling the speed. Poor precision in the torque control at the time of low speeds causes degradation in the reproducibility at the time of starting or stopping the driving operation or in the driving operations in summer and in winter, resulting in difficulty in adjusting the torque control.
The present invention has been achieved in order to solve the above problems. It is an object of this invention to provide a control device for an induction motor which applies two square matrixes that can optimally suppress influences of motor constant errors in resistors, etc. to an amplifying unit 6 so that torque errors caused by the influences of motor constant errors in resistors, etc., are properly suppressed, and a control method for such a device.
In order to solve this problem, the control device for an induction motor according to the present invention is provided with a rotation speed detector which detects the rotation speed of an induction motor, a current detector which detects a primary current of the induction motor, an amplifying unit which amplifies a deviation between an estimated primary current obtained from a magnetic flux observing device and the primary current obtained by the current detector, a magnetic flux observing device which estimates an estimated secondary magnetic flux and an estimated primary current of the induction motor based upon the rotation speed obtained from the rotation speed detector, the primary voltage of the induction motor and the deviation signal obtained from the amplifying unit, and a control unit which controls a voltage to be applied to the induction motor based upon the estimated secondary magnetic flux obtained from the magnetic flux observing device, and in this arrangement, the amplifying unit is allowed to amplify the deviation of the primary current based upon two square matrixes H1, H2 that do not satisfy a commutative rule, that is, feedback gains consisting of 8 respectively independent factors, therefore, without the limitation of having to place the pole of the magnetic flux observing device on the conjugate complex pole or the duplex pole, it is possible to reduce degradation in the torque control precision caused by the motor constant errors.
According to the control device for an induction motor of the next invention, in the above invention, the amplifying unit determines the feedback gain based upon the rotation angular velocity, therefore, even when a variable speed driving operation is conducted, it is possible to suppress degradation in the torque control precision caused by the motor constant errors.
According to the control device for an induction motor of the next invention, in the above invention, the amplifying unit determines the feedback gain based upon a sliding angle frequency, therefore, even when a load torque varies, it is possible to suppress degradation in the torque control precision caused by induction motor constant errors.
According to the control device for an induction motor of the next invention, in the above invention, based upon both of the rotation angular velocity and the sliding angle frequency, the amplifying unit determines the feedback gain so that even when a variable-speed operation is conducted or the load torque varies, it is possible to suppress degradation in the torque control precision caused by induction motor constant errors.
According to the control device for an induction motor of the next invention, in the above invention, the amplifying unit is allowed to amplify the primary current based upon a feedback gain   "AutoLeftMatch"      (                                        H            1                                                            H            2                                )  
consisting of 8 independent elements that satisfy the following equations, therefore, it is possible to suppress degradation in the torque control precision caused by any motor constant errors,       (                                        H            1                                                            H            2                                )    =                    PC                              xe2x80x83                    ⁢          τ                    ⁡              (                              D            2                    ⁢                      D            2            τ                          )                    -      1      
where,                     PA        τ            +      AP      -                                                  PC                                                xe2x80x83                                ⁢                τ                                      ⁡                          (                                                D                  2                                ⁢                                  D                  2                  τ                                            )                                            -            1                          ⁢        CP            +                        B          2                ⁢                  B          2                                    xe2x80x83                        ⁢            τ                                =    0        A    =          (                                                  a              11                                            ω                                              a              12                                            0                                                              -              ω                                                          a              11                                            0                                              a              12                                                                          a              21                                            0                                              a              22                                                          ω              -                                                P                  m                                ⁢                                  ω                  m                                                                                          0                                              a              21                                                          -                              (                                  ω                  -                                                            P                      m                                        ⁢                                          ω                      m                                                                      )                                                                        a              22                                          )            C    =          (                                                  c              1                                            0                                              c              2                                            0                                                0                                              c              1                                            0                                              c              2                                          )                                                a            11                    =                                    -                              ζ                                  -                  1                                                      ⁢                          L              r                        ⁢                          R              s                                                                                a            12                    =                                    ζ                              -                1                                      ⁢                          MR              s                                                                                a            21                    =                                    ζ                              -                1                                      ⁢                          MR              r                                                                                a            22                    =                                    -                              ζ                                  -                  1                                                      ⁢                          L              s                        ⁢                          R              r                                                                                c            1                    =                                    ζ                              -                1                                      ⁢                          L              r                                                                                c            2                    =                                    -                              ζ                                  -                  1                                                      ⁢            M                                                        ζ          =                                                    L                s                            ⁢                              L                r                                      -                          M              2                                          
B2: arbitrary matrix,
D2: arbitrary matrix,
xcfx89: primary angular velocity of the induction motor
xcfx89m: rotation angular velocity of the induction motor
xcfx89s: sliding angular velocity of the induction motor
Pm: polar logarithm
Rs: primary resistance value of the induction motor
Rr: secondary resistance value of the induction motor
Ls: primary inductance value of the induction motor
Lr: secondary inductance value of the induction motor
M: mutual inductance value of the induction motor.
According to the control device for an induction motor of the next invention, in this invention, the amplifying unit is allowed to amplify the deviation of the primary current based upon a feedback gain   "AutoLeftMatch"      (                                        H            1                                                            H            2                                )  
consisting of 8 independent elements that satisfy the following equations, therefore, it is possible to suppress degradation in the torque control precision caused by any primary resistance errors and secondary resistance errors,       (                                        H            1                                                            H            2                                )    =                    PC                              xe2x80x83                    ⁢          τ                    ⁡              (                              D            2                    ⁢                      D            2            τ                          )                    -      1      
where                               a          11                =                              -                          ζ                              -                1                                              ⁢                      L            r                    ⁢                      R            s                                                            a          12                =                              ζ                          -              1                                ⁢                      MR            s                                                            a          21                =                              ζ                          -              1                                ⁢                      MR            r                                                            a          22                =                              -                          ζ                              -                1                                              ⁢                      L            s                    ⁢                      R            r                                                            c          1                =                              ζ                          -              1                                ⁢                      L            r                                                            c          2                =                              -                          ζ                              -                1                                              ⁢          M                                                  ζ          =                                                    L                s                            ⁢                              L                r                                      -                          M              2                                      ⁢                  
                ⁢                                            PA              τ                        +            AP            -                                                                                PC                                                                  xe2x80x83                                            ⁢                      τ                                                        ⁡                                      (                                                                  D                        2                                            ⁢                                              D                        2                        τ                                                              )                                                                    -                  1                                            ⁢              CP                        +                                          B                2                            ⁢                              B                2                τ                                              =          0                ⁢                  
                ⁢                              A            xe2x80x2                    =                      (                                                                                a                    11                                                                    ω                                                                      a                    12                                                                    0                                                                                                  -                    ω                                                                                        a                    11                                                                    0                                                                      a                    12                                                                                                                    a                    21                                                                    0                                                                      a                    22                                                                                        ω                    -                                                                  P                        m                                            ⁢                                              ω                        m                                                                                                                                          0                                                                      a                    21                                                                                        -                                          (                                              ω                        -                                                                              P                            m                                                    ⁢                                                      ω                            m                                                                                              )                                                                                                            a                    22                                                                        )                          ⁢                  
                ⁢                              B            2                    =                      (                                                                                R                    s                                                                                                                                                                  R                        s                                                                    R                        r                                                              ⁢                                                                  L                        r                                            ⁡                                              (                                                  ω                          -                                                                                    P                              m                                                        ⁢                                                          ω                              m                                                                                                      )                                                                                                                                          0                                                                                                  -                                          M                      ⁡                                              (                                                  ω                          -                                                                                    P                              m                                                        ⁢                                                          ω                              m                                                                                                      )                                                                                                                  )                          ⁢                  
                ⁢                  C          =                      (                                                                                c                    1                                                                    0                                                                      c                    2                                                                    0                                                                              0                                                                      c                    1                                                                    0                                                                      c                    2                                                                        )                          ⁢                  
                ⁢                              D            2                    =                      (                                                            ϵ                                                  0                                                                              0                                                  ϵ                                                      )                              
xcex5: arbitrary positive value.
According to the control device for an induction motor of the next invention, in the above invention, the amplifying unit is allowed to amplify the deviation of the primary current based upon a feedback gain   "AutoLeftMatch"      (                                        H            1                                                            H            2                                )  
consisting of 8 independent elements that satisfy the following equations, therefore, it is possible to suppress degradation in the torque control precision caused by any secondary resistance errors,       (                                        H            1                                                            H            2                                )    =                    PC                              xe2x80x83                    ⁢          τ                    ⁡              (                              D            2                    ⁢                      D            2            τ                          )                    -      1      
where                     PA        T            +      AP      -                                                  PC                                                xe2x80x83                                ⁢                τ                                      ⁡                          (                                                D                  2                                ⁢                                  D                  2                  τ                                            )                                            -            1                          ⁢        CP            +                        B          2                ⁢                  B          2          τ                      =    0              A      xe2x80x2        =          (                                                  a              11                                            ω                                              a              12                                            0                                                              -              ω                                                          a              11                                            0                                              a              12                                                                          a              21                                            0                                              a              22                                                          ω              -                                                P                  m                                ⁢                                  ω                  m                                                                                          0                                              a              21                                                          -                              (                                  ω                  -                                                            P                      m                                        ⁢                                          ω                      m                                                                      )                                                                        a              22                                          )                  B      2        =          (                                    0                                                0                                                0                                                1                              )            C    =          (                                                  c              1                                            0                                              c              2                                            0                                                0                                              c              1                                            0                                              c              2                                          )                  D      2        =          (                                    ϵ                                0                                                0                                ϵ                              )      
xcex5: arbitrary positive value.